1. Field of the Invention
This invention relates to a process of making steel by melting sponge iron in an electric arc furnace, which sponge iron is produced by direct reduction.
2. Discussion of Prior Art
It is known that difficulties will be encountered when an electric arc furnace is charged only with sponge iron (direct reduced iron). These difficulties are due to the low density and the low conductivity of the sponge iron. Nevertheless, it is desired to use mainly sponge iron in an electric arc furnace. In that case it is advantageous to maintain in the furnace a pool of carbon-containing liquid iron (hot metal), to charge the sponge iron onto said pool and to supply most of the additional energy via said pool (hot metal process).
But even in that hot metal process the electric arc furnace must be completely emptied after two or three charges so that the lining can be repaired. As a result, the furnace cannot be continuously operated in that hot metal process since a new pool must be formed whenever the furnace has been emptied. For this reason the advantages which are inherent in that process cannot be fully utilized unless molten iron is available from another source, preferably from a blast furnace. But this option is very unlikely in a plant for processing sponge iron.
Additionally, the energy consumption of an electric arc furnace exhibits large fluctuations owing to the characteristic mode of operation and furthermore owing to the discontinuous mode of operation of the electric arc furnace. These fluctuations refer to the rate at which energy is consumed and to the total quantity of energy which is consumed. The electric power supply system powering an electric arc furnace must be so powerfull that the reaction which is due to the furnace operation does not exceed the permissible limits.